This invention relates to polymerization catalysts for unsaturated monomers, novel transition metal compounds, polymerization processes using the same, and copolymers having a linkage formed by the migration of the active hydrogen of an unsaturated monomer. More particularly, it relates to polymerization catalysts for unsaturated monomers comprising organic transition metal complexes having a specific structure, processes for polymerizing unsaturated monomers by using such polymerization catalysts, and copolymers having a linkage formed by the migration of the active hydrogen of an unsaturated monomer.
A large number of catalysts for the polymerization of unsaturated monomers have been reported by many investigators for long time. These catalysts are used by selecting an appropriate one so as to suit the type of the unsaturated monomer to be polymerized. According to the mechanism of polymerization, they are broadly classified into cationic polymerization catalysts, coordinated anionic polymerization catalysts and anionic polymerization catalysts.
The cationic polymerization of a-olefins, styrene, vinyl ether, vinyl sulfide and the like by using cationic polymerization catalysts such as proton acids (e.g., sulfuric acid and trifluoroacetic acid) and Lewis acids (e.g., aluminum chloride and titanium tetrachloride) is generally known. Moreover, as catalyst systems comprising a combination of an alkyl compound of a metal of group I, II or XIII of the periodic table and a compound of a transition metal of group IV to X are known as Ziegler-Natta catalysts for the coordinated anionic polymerization of ethylene, xcex1-olefins, dienes and the like [John Boor, Jr., Ziegler-Natta Catalysts and Polymerizations, Academic Press, Inc. (1979)]. Furthermore, polymerization catalysts for olefins comprising organic transition metal complexes containing a transition metal of group IV, VIII or X have recently been reported by W. Kaminsky (Angew. Chem., 1985, 97, 507) and M. Brookhart (J. Am. Chem. Soc., 1995, 117, 6414; 1998, 120, 4049). These organic transition metal complexes are catalyst systems in which methylaluminoxane is used as a Lewis acid co-catalyst.
Furthermore, polymerization catalysts for olefins comprising organic transition metal complexes containing a transition metal of group IV, VIII or X have recently been reported by W. Kaminsky (Angew. Chem., 1985, 97, 507) and M. Brookhart (J. Am. Chem. Soc., 1995, 117, 6414; 1998, 120, 4049). These organic transition metal complexes are catalyst systems in which methylaluminoxane is used as a Lewis acid co-catalyst.
Furthermore, it is also known that basic catalysts such as butyllithium, naphthalenesodium and butoxysodium catalyze the anionic polymerization of unsaturated monomers such as methacrylic esters and so on having an electron-withdrawing polar group and other unsaturated monomers such as xcex1-olefins, dienes and styrene.
With respect to the hydrogen migration polymerization of acrylamide, a process for synthesizing poly-xcex2-alanine (or Nylon-3) from acrylamide with the aid of a basic catalyst such as tert-butoxysodium was first reported by Matlack (U.S. Pat. No. 2,672,480) and Breslow (J. Am. Chem. Soc., 1957, 79, 3760). Since then, many improvements in basic catalysts and polymerization processes have been made. As such polymerization catalysts, alkali metal alcoholates such as tert-butoxypotassium (Japanese Patent Publication Nos. 27616/""68, 21739/""71 and 37359/""73), alkyl alkali metals such as butyllithium (U. Morgenstern et al., Makromol. Chem., 1992, 193, 2561), and Grignard reagents such as ethylmagnesium bromide (Ogata, J. Polymer Sci., 1960, 147, 271) have been reported.
Moreover, recently, the polymerization of methyl methacrylate by using a lanthanide-based metallocene compound having a ligand comprising a cyclic hydrocarbon having xcfx80-electrons (e.g., a pentamethylcyclopentadienyl ligand) has been reported by Yasuda et al. (Macromolecules, 1993, 26, 7134), and the polymerization of styrene, or the copolymerization of styrene and caprolactone, with the aid of a lanthanide-based organometallic complex having an amide ligand has been reported (Japanese Patent Laid-Open No. 241314/""97). Furthermore, the polymerization of acrylonitrile with the aid of a cobalt-phosphine complex catalyst has been reported (K. Tsuchihara et al., Chemistry Letters, 1999, 9, 891). In addition, the use of an yttrium complex catalyst containing crosslinked cyclopentadiene and butylamide for the polymerization of ethylene or styrene (J. Okuda et al., Organometallics, 2000, 19, 228) and for the polymerization of acrylonitrile or butyl acrylate (J. Okuda et al., Polymer Preprints, 1999, 1, 372) have also been reported. On the other hand, these complex catalysts have low polymerization activity, particularly for acrylonitrile, and the molecular weights of the resulting polymers are low. Moreover, since they have no ability to induce copolymerization, no copolymerization occurs even between acrylonitrile and styrene.
However, for the anionic polymerization of unsaturated monomers, only organometallic compounds based on an alkali metal or alkaline earth metal are known as basic catalysts for polymerizing a relatively wide range of unsaturated monomers such as acrylamide, acrylonitrile, methacrylic esters, styrene and dienes, and only lanthanide-based metallocene compounds and limited organometallic complexes are known as catalysts for the polymerization of methacrylic esters. With respect to other metals, there has been found no organic transition metal complex catalyst that has polymerization catalyst characteristics permitting the polymerization of not only monomers containing a functional group with high polarity (e.g, acrylamide and acrylonitrile) but also monomers containing a functional group with medium polarity (e.g, methacrylic esters) and monomers having low polarity (e.g., styrene), and also has the ability to copolymerize these monomers. Moreover, conventional basic catalysts based on an alkali metal or alkaline earth metal and conventional limited organometallic complexes tend to have low polymerization activity and low polymer yield, and the molecular weights of the resulting polymers are low in many cases.
In order to solve the above-described problems, the present inventors made intensive investigations on polymerization catalysts for unsaturated monomers, polymerization processes using them, and copolymers having a polyamide linkage, and have now completed the present invention.
That is, the present invention relates to polymerization catalysts for unsaturated monomers which are represented by the following general formula [1]:
MR1kR2mR3nQhxe2x80x83xe2x80x83[1]
wherein R1 is selected from ligands having at least one nitrogen, sulfur, phosphorus or oxygen atom; R2 is selected from ligands comprising cyclic hydrocarbons having xcfx80-electrons, and R1 and R2 may be crosslinked with each other; R3 is selected from ligands comprising a hydrogen atom, alkyl groups, aryl groups, silicon-containing alkyl groups and silicon-containing aryl groups; M is a metal selected from the metals of group III of the periodic table; Q is selected from halogen atoms and electron-donating ligands, where Q may be the same or different if h is more than one; k is an integer of 1 to 4; and m, n and h are each 0 or an integer of 1 to 4. The present invention also relates to novel transition metal compound of the general formula [1] in which R1 is a ligand represented by the following general formula [2], [3] or [4]: 
wherein R4 is selected from a hydrogen atom, alkyl groups and aryl groups; R5 and R6 are each selected from alkyl groups, aryl groups, silicon-containing alkyl groups and silicon-containing aryl groups; X1 is selected from a carbon atom and a silicon atom, where X1 may be the same or different if X1 is more than one and i is an integer of 1 to 6. 
wherein R7, R8 and R9 are each selected from alkyl groups, aryl groups, silicon-containing alkyl groups and silicon-containing aryl groups, where R7, R8 and R9 may be the same or different if j is more than one; and j is 0 or an integer of 1 to 4. 
wherein R10 is selected from a hydrogen atom, alkyl groups and aryl groups; R11, R12, R13 and R14 are each selected from alkyl groups, aryl groups, silicon-containing alkyl groups and silicon-containing aryl groups; X2 is selected from a carbon atom and a silicon atom, where X2 may be the same or different if 1, p and q is more than one; and 1, p and q are each 0 or an integer of 1 to 4.
Moreover, the present invention also relates to a polymerization process comprising the step of effecting the homopolymerization or copolymerization of one or more unsaturated monomers by using a polymerization catalyst of the general formula [1] in which R1 is a ligand represented by the general formula [2], [3] or [4]. Furthermore, the present invention also relates to a polymerization process comprising the step of effecting the homopolymerization of an unsaturated monomer having a cyano group, or the copolymerization of unsaturated monomers including at least one unsaturated monomer having a cyano group, with the aid of a polymerization catalyst of the general formula [1] in which m is 0, and to a polymerization process comprising the step of effecting the homopolymerization of an unsaturated monomer having an amide group, or the copolymerization of unsaturated monomers including at least one unsaturated monomer having an amide group, with the aid of a polymerization catalyst of the general formula [1].
Furthermore, the present invention also relates to copolymers formed by the copolymerization of unsaturated monomers including at least one unsaturated monomer having active hydrogen, and characterized by having a linkage formed by the migration of the active hydrogen of the unsaturated monomer.